It is our goal to continue our molecular and genetic analysis of synaptic transmission in the soil nematode Caenorhabditis elegans. C. elegans is being used for these studies because of its simple nervous system, its ease of genetic and molecular analysis, and the complete sequencing of its genome. The proposed research is based on recent results and on recent technological advances. The three broad goals are: (1) to analyze in depth the recently-described rip-1 gene, which encodes an extremely large protein thought to provide a "molecular scaffold" for the components of a presynaptic nerve terminal; (2) to begin an investigation of the mechanisms used within nerve terminals to regulate the amount of neurotransmitter packaged into each synaptic vesicle; and (3) to continue studies using a C. elegans cell culture system for the analysis of synaptic development and function in vitro. The proposed studies will extend our previous analysis of synaptic structure and neurotransmitter function in the soil nematode Caenorhabditis elegans, and will include the isolation of mutants deficient in the regulation of vesicle content, and the identification of specific molecules and signaling pathways required for proper modulation of quantal size. Although this is basic research, it is clearly relevant to health, since proper neurotransmitter release is crucial to proper function of the nervous system, and defective transmitter release has been implicated in many psychiatric and neurological disorders.